1. Field of the Invention
This invention relates to derrick mounted apparatus useful in the manipulation of lengths of pipe in or out of one or more finger boards in proximity thereto; more particularly, this invention relates to such derrick mounted apparatus including a pipe manipulating arm and a pipe gripping hand rotatably attached to one end thereof.
2. Description of the Prior Art
During the drilling of an oil well utilizing a rotary tool drilling rig, it is necessary from time to time to connect additional joints or lengths of drill pipe to the upper end of the drill string as the well is extended into the ground. Likewise, when the drilling operation is completed, lengths of drill pipe are periodically disconnected from the upper end of the drill string as the pipe is removed from the well. In the connecting of a length of pipe to the drill string, the length of pipe is vertically supported from a traveling block which normally is provided in a hoisting derrick erected over a rotary table used to rotate the drill string and thereby a rotary drilling tool secured to the lower end of the drill string. A similar vertical supporting of the drill pipe takes place when disconnecting lengths of pipe. The length of pipe which is vertically supported is generally of very substantial weight.
Originally, suspended lengths of pipe were moved manually into position for engagement with the upper end of the drill string projecting above the rotary table and likewise moved manually from engagement with the drill string to an area for storage. Due to considerations of personnel safety, particularly in connection with operations performed on floating vessels and with offshore platforms, where such manual operations can be quite hazardous, various devices have been developed to mechanically constrain and controllably move a vertically supported length of pipe in a drilling rig, both to connect and after disconnection of the length of pipe from the drill string.
The devices which have been proposed have generally been proposed for installation on the rig floor. Such devices are capable of grasping a length of pipe, rotating the length of pipe into the desired position, and finally, positioning the length of pipe for connection to the drill string. Typical examples of such rig floor mounted devices can be found in U.S. Pat. No. 2,450,934 to Calhoun and U.S. Pat. Nos. 3,371,728 and 3,477,527 assigned to Global Marine. A problem, however, still arises with respect to proper grasping and positioning of the upper portion of the length of pipe.
Lengths of pipe which are to be later attached to the drill string or which have been disconnected from the drill string are typically held in a racking board assembly attached to the upper portion of the derrick. One device which has been previously proposed for the manipulation of the drill pipe in or out of the racking board is illustrated, for example, in U.S. Pat. No. 2,416,815 to Calhoun. This patent illustrates an apparatus with pipe engaging jaws attached to an arm which provides for retraction of the jaws and release of a pipe engaged thereby, the entire assembly being mounted on the derrick adjacent the racking board. Certain limitations are inherent in this device, however, in that the pipe engaging jaws work only to release or engage the lengths of pipe and the jaws or head section of the apparatus are not capable of movement independent of the arm or body of the device to provide the desired flexibility in orientation and manipulation of the drill pipe. These deficiencies have made the type of device illustrated in the Calhoun patent somewhat less than satisfactory.
A further derrick mounted device for manipulating lengths of pipe in or out of a racking board is a device manufactured by Bryon Jackson, Inc., illustrated for example in Composite Catalog of Oil Filed Equipment and Services, 31st revision, 1974-75, Vol. 1, pp. 820-821. This device includes an upper racker and associated racking board, the racker consisting of a carriage which travels across the width of the derrick on tracks and an arm which is powered toward and away from the centerline of the well through the carriage and a hand fitted to the end of the arm.
This device, like the device of Calhoun, is quite complicated and does not allow independent directional rotation of the hand. All of the directional orientation of the hand is associated with movement of the entire arm on a carriage. The complexity of this device makes it very difficult to modify a well derrick in the field to include the device. This device, therefore, is also less than completely satisfactory.